Examples of a pipe part suitable for conveying a solid particulate material at low to moderate pressure (i.e. up to about 15 bar) are described in U.S. Pat. No. 6,227,768, DE 12 69 571 and WO 2004/087331.
The pipe part disclosed in U.S. Pat. No. 6,227,768 includes an inner conduit adapted for transporting particulate material from the first end to the second end of the conduit and having a gas permeable wall, which inner conduit is longitudinally disposed in an outer conduit having an impermeable wall. The outer conduit in first and second ends is provided with inwardly protruding sealing support rings wherein the inner conduit is rigidly fixed in the outer conduit so that a gas distribution chamber is situated between the outer conduit and the inner conduit and the inwardly protruding sealing support rings. A compressed gas inlet nozzle traverses the outer conduit and a gas pressure source is attached to the gas inlet nozzle conveying gas to the gas distribution chamber and through the gas permeable wall.
A pipe part as disclosed in U.S. Pat. No. 6,227,768 can be used in a pipe system for transporting loads of solid particulates such as powders at relatively moderate temperatures and pressures. Such a pipe systems can for instance be provided downstream of a storage silo or a hopper for particulate materials.
In operation, the external gas pressure traverses the gas permeable inner conduit to assist the transport of the resident or entrained particulate materials.
When the pipe part as disclosed in U.S. Pat. No. 6,227,768, is connected with other pipes sufficiently tight to contain elevated pressures and or temperatures, it is anticipated that the inner conduit will damage under mechanical loads resulting from the connections.
Depending on the materials used, axial loading resulting from differences in thermal expansion between the inner and outer conduits might lead to damage of the inner conduit.
The above is even more pertinent in case the pipe part is to be used in a pipe system for transporting pulverised coal and fly ash in coal gasification plants. Coal gasification is known in the art and involves the partial combustion of solid particulate carbonaceous materials such as coal, petroleum coke and biomass. The partial combustion process is generally carried out at elevated pressures that may be as high as 80 or even 100 bar and at elevated temperatures. Therefore, the pipe system must be suitable for exposure to elevated temperature and/or pressure.
Moreover, replacement of the inner conduit of the known pipe part is cumbersome.
Furthermore, inspection of the inner conduit of the known pipe part is only possible from one side.
It is an object of the present invention to minimize one or more of the above drawbacks.
It is a further object of the present invention to provide an alternative pipe part that can be exposed to elevated temperatures and/or pressures.